The Main Causes of Bacterial Colonization in Endotracheal Tubes and Tracheal Secretions in Neonates Admitted to the Neonatal Intensive Care Unit.

Background
Ventilator-associated pneumonia (VAP) is the second most common nosocomial infection in neonates, admitted to neonatal intensive care units (NICUs). The aim of this study was to identify the main causes of bacterial colonization in endotracheal tubes and tracheal secretions of neonates hospitalized in the NICUs of our university hospitals.


Materials and Methods
This cross sectional study was conducted during 2015-2016. Thirty-nine neonates, who were under mechanical ventilation in the NICUs of Baqiyatallah and Najmiyeh hospitals of Tehran, Iran, were assessed. The patients were selected using the census sampling method. Gestational age, birth weight, duration of mechanical ventilation, length of hospital stay, tracheal discharge culture, endotracheal tube culture, blood culture, and chest radiography were evaluated.


Results
In a total of 39 neonates (50.3% males and 49.7% females) with the mean age of 1.17±1.12 days, bacterial growth was reported in 6 (15.3%) cases. The antibiotic study of tracheal secretion and endotracheal tube cultures showed that 2.6% of patients were resistant to cephalosporins, aminoglycosides, nitrofurantoin, and carbapenem. Moreover, 12.8% were also resistant to fluoroquinolones, besides these antibiotics.


Conclusion
Tracheal secretion culture is a simple and proper approach for the diagnosis of VAP. Besides reducing the costs, this method can play a significant role in decreasing the incidence of infections.


INTRODUCTION
Ventilator-associated pneumonia (VAP) is defined as nosocomial pneumonia in mechanically ventilated patients, which often occurs within 48 hours after the initiation of mechanical ventilation (1). It is the second most common nosocomial infection in infants and is associated with increased length of hospital stay, leading to high morbidity and mortality among neonatal intensive care unit (NICU) patients, with an estimated incidence of 6-32% (2)(3)(4)(5). The origins of VAP are aspiration of secretion, colonization of the airways, use of contaminated instruments, and medications (6). negative bacteria are the most commonly isolated causative organisms, while Gram-positive bacteria have become increasingly more common over the past several years (7,8). The clinical criteria for the diagnosis of VAP have been established by the National Nosocomial Infection Surveillance System (NNIS) and the Center for Disease Control and Prevention (CDC) (9). However, it should be noted that there is no current gold standard for the diagnosis of VAP in neonates (1,10).
The aim of this study was to identify the main causes of bacterial colonization in endotracheal tubes and tracheal secretions of neonates, hospitalized in the NICUs of our university hospitals.  (11).

MATERIALS AND METHODS
In this study, the specimen inside the sterilized centrifuge tube, along with 1 cc of sterile physiological saline or normal sterile saline, was centrifuged for 10 minutes at 2000-2500 rpm. In addition, eosin methylene blue and blood agar media were used. The positive samples (>10 5 bacterial colonies) were transferred to Mueller-Hinton Agar for antibiogram studies. Gestational age, birth weight, duration of mechanical ventilation, length of hospital stay, tracheal discharge culture, endotracheal tube culture, blood culture, and chest radiography were also evaluated. The results were confirmed by a laboratory technologist with 10 years of relevant experience.
All neonates, aged 1 to 28 days with at least 48 hours of mechanical ventilation, were enrolled in this study. The parents completed the informed consent forms for participation in the study. On the other hand, the do-notresuscitate (DNR) and near-death patients, as well as those with less than 48 hours of mechanical ventilation, were excluded from the study. Patients with cardiovascular diseases, electrolyte imbalance, respiratory distress syndrome, and other underlying pulmonary problems were also excluded.

Statistical analysis
Data were analyzed using SPSS version 16 for Windows (SPSS Inc. Chicago, IL). Variables with a normal distribution, according to one-sample Kolmogorov-Smirnov test, were compared using independent sample t test between the groups and paired sample t test within the groups. Chi square test was also used to compare categorical variables in the groups. P-value less than 0.05 was considered statistically significant.

Ethical considerations
This study was approved by the Ethics Committee of

Baqiyatallah University of Medical Sciences and Health
Services. The parents were asked to sign an informed consent form before completing the questionnaires. All terms of the Declaration of Helsinki were considered, and the patients' personal information remained anonymous.     In Table 3, some of the studies in this field have been compared (12)(13)(14)(15)(16). Some studies (13,14)

CONCLUSION
We concluded that evaluation of tracheal secretion culture is a simple and proper strategy for the diagnosis of VAP. Considering the increased risk of infection in many intubation and extubation procedures, this approach, in addition to reducing the costs, can play a significant role in reducing the incidence of infections.